The actor, 40, has confirmed that wife Luciana Barroso is expecting a baby girl - her fourth.
The Oscar winner, who filmed an appearance on the Late Show with David Letterman in New York yesterday, is already father to Isabella, four, and Gia, two, and stepfather to Alexia, 11, Luciana's daughter from a previous relationship.
Man of the house: Matt Damon, pictured at the Late Show with David Letterman yesterday, has revealed his wife Luciana is expecting her fourth baby girl
'Raising girls is amazing. It's a whole new world. There's a lot of princess outfits, not for me though.
'There are huge differences amongst the girls, kids are amazing like that, same parents, same environment but they're all different.
'And with each one it becomes exponentially more complicated.'
'It's a girl!' The actor joked about princess outfits with host David Letterman, and also praised best friend Ben Affleck's recent success with The Town
'But with girls it's totally different. They're a different species altogether so I'm learning.'
The actor joked with host David Letterman during his appearance on his show last night, where he impersonated Matthew McConaughey and praised best friend Ben Affleck's new film The Town.
'Thrilled': The 40-year-old Invictus star is already father to Isabella, four, Gia, two, pictured in April, and stepfather to Alexia, 11
On Sunday, Luciana, 39, accompanied her husband to the New York Festival premiere of the film, helmed by his Invictus director Clint Eastwood.
And while dressing during pregnancy can be difficult for some, Miss Barroso looked effortlessly glamorous in a leopard print dress.
Hereafter tells three parallel stories of three different people all affected by death in some way.
Matt plays a man who can communicate with the dead in the film which opens in the U.S. on October 15.
The couple announced the exciting news that they were expecting another baby together back in April.
Ready for her close-up: The couple are now bracing themselves for their 'next little tornado'
And he has said: 'We're bracing ourselves for our next little tornado.'
He told People: 'She really keeps it together. We just talk it out and work it all out.
'You say, this is the job and this is the time commitment and this is where it will be. I’m a lot easier to hire if you’re doing movies in New York.'
Star power: Damon with co-stars Bryce Dallas Howard, Cecile de France and director/producer Clint Eastwood at the closing night premiere of Hereafter
